L3- Hypothalamic-Pituitary Relationship Flashcards

1
Q

What is the main role of the hypothalamus?

A

The hypothalamus integrates signals from other brain regions to stimulate the release of hypothalamic-releasing hormones.

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2
Q

What is the organization of the hypothalamus?

A

The hypothalamus is divided into discrete hypothalamic nuclei.

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3
Q

What is the median eminence?

A

ME- the median eminence, is one of the hypothalamic nuclei.

It makes up the floor of the hypothalamus, and serves as a convergence point for axons.

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4
Q

Sleep is regulated by which hypothalamic nuclei?

A

The Suprachiasmatic nucleus (SCN)

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5
Q

Feeding behavior/satiety is regulated by which hypothalamic nuclei?

A

Arcuate nucleus (ARC)

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6
Q

Thirst is regulated by which hypothalamic nucleus?

A

Paraventricular Nucleus- PVN

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7
Q

Reproduction is regulated by which hypothalamic nuclei?

A

Preoptic nucleus (POA)

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8
Q

Circadian rhythms are regulated by which hypothalamic nuclei?

A

Suprachiasmatic nuclei (SCN)

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9
Q

Mood/emotion/stress are regulated by which hypothalamic nuclei?

A

Paraventricular nucleus and arcuate nucleus

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10
Q

Body temperature is regulated by which hypothalamic nucleus?

A

Preoptic nucleus (POA)

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11
Q

Blood pressure is regulated by which hypothalamic nucleus?

A

Paraventricular nucleus (PVN)

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12
Q

GnRH and GnIH are released from what hypothalamic nuclei?

A

Scattered, but the majority are from the POA (preoptic)

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13
Q

CRH (corticotropin releasing hormone) is released from which hypothalamic nuclei?

A

Paraventricular Nucleus - PVN

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14
Q

TRH peptide is released from which hypothalamic nucleus?

A

PVN

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15
Q

GHRH is released from which hypothalamic nuclei?

A

Arcuate nucleus

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16
Q

Somatostatin (GHRH inhibitor) is released from which hypothalamic nuclei?

A

Periventricular (PeVN)

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17
Q

Dopamine is released from which hypothalamic nuclei?

A

Arcuate Nucleus

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18
Q

How big is TRH? What are its second messengers?

A

TRH is 3 amino acids (tiny) –> shorter half-life

TRH uses IP3/DAG/PKC as second messengers

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19
Q

How big is GnRH? What are its second messengers?

A

GnRH is 10 amino acids –> medium sized

GnRH uses IP3/DAG/PKC as second messengers

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20
Q

How big is CRH? What are its second messengers?

A

CRH is 41 amino acids –> large

CRH uses cAMP as second messengers

21
Q

How big is GHRH? What are the second messengers?

A

GHRH is 44 amino acids–> large

GHRH uses cAMP as a second messenger

22
Q

How big is GHIH (somatostatin)? What are the second messengers?

A

GHIH is 14 amino acids –> medium

GHIH/somatostatin uses cAMP as a second messenger

23
Q

Describe the prevalence of GnRH producing cell bodies?

A

Relatively few

24
Q

Where do the very long axons of the GnRH cell bodies extend to?

A

THe median eminence

25
Describe the timing of the GnRH release
GnRH is released in a pulsatile manner.
26
What is Kallman Syndrome?
Rare genetic disease in which GnRH neurons fail to enter the CNS. It is characterized by reproductive failure and anosmia (inability to smell) This is a heritable as either an X-linked or autosomal problem
27
What is the hypophysial portal system?
A vascular connection between the hypothalamus and the pituitary gland
28
Explain the importance of hypothalamic and pituitary pulsatility.
The rate of GnRH pulsatility directly affects the release of LH and FSH release from the anterior pituitary Fast pulse --> more LH Slow pulse --> more FSH
29
Through what subunit are the different anterior pituitary hormones differentially regulated by GnRH release?
the beta-subunit. TSH, FSH, LH and hCG all share a common alpha subunit, and the beta subunits are regulated by their respective hypothalamic-releasing hormones
30
What is the difference between the tuberoinfundibular system and the neurohypophysial tract?
Tuberoinfundibular system: comprises all neurons that send axonal projections to the median eminence. Hormones target the anterior pituitary through the capillary system (endocrine). Neurohypophysial tract: comprises neurons whose axons terminate in the posterior pituitary (no NOT have a portal system)
31
What is another name for pituitary?
Hypophysis
32
What are the three anatomical divisions of the anterior pituitary?
``` Pars distalis (90%) Pars tuberalis Pars intermedia ```
33
What are the two anatomical divisions of the posterior pituitary?
Pars nervosa | Infundibulum (stalk)
34
Differentiate the type of tissue in the anterior vs posterior pitutiary
Anterior: glandular tissue- cords of epithelial cells Posterior: neural tissue (terminal axons and glial cells- part of neurohypophysial tract)
35
What is another name for posterior pituitary?
Neurohypophysis
36
Magnocellular neurons are found in which hypothalamic nuclei?
The Paraventricular nucleus (PVN)
37
Axons from magnocellular neurons terminate where?
Neurohypophysis (posterior pituitary)
38
What are the major hormones released from the posterior pituitary?
Arginine vasopressin (AVP/ADH) and oxytocin
39
How do hormones from the posterior pituitary enter systemic circulation?
The neurohypophysis has it's own capillary bed. The terminal axons of the magnocellular neurons release AVP and OXY directly into the blood stream Axons terminate near fenestrated capillaries
40
What are Herring bodies?
Herring bodies are dilations of unmyelinated axons near the terminals of magnocellular axons in the posterior pituitary. This is the site of hormone release
41
Name 3 types of anterior pituitary cell types. Differentiate them by color following staining.
Acidophils (light stain), Basophils (dark stain) and Chromophobes (clear)
42
What hormones are released from acidophils in the anterior pituitary?
Somatotrophs- GH | Lactotrophs- Prolactin
43
What hormones are released from basophils in the anterior pituitary?
Corticotrophs- ACTH Gonadotrophs- LH/FSH Thyrotrophs- TSH
44
What is released from the chromophobes of the anterior pituitary?
Paracrine actions- health maintenance of the other pituitary cells
45
Discuss the relative position of the median eminence and the blood brain barrier
The median eminence lies outside the blood brain barrier - signals that regulate the ME can come from the periphery as it doesn't have to cross the blood brain barrier
46
Discuss the distribution of anterior pituitary hormone cell distributions
Cells cluster in regions- (regional distribution)
47
Axons release hormones from the hypophysial portal system to the anterior pituitary where?
At the median eminence. They travel throughout the anterior pituitary via the hypophysial portal system
48
How does the release of most pituitary hormones vary throughout the day?
Most pituitary hormones have a circadian rhythm - this is important and must be considered when taking blood samples to evaluate endocrine disease.